Use the same string for typevars as Python so it looks similar

Author: saulshanabrook

python/egglog/declarations.py

@@ -312,7 +312,7 @@ def to_just(self) -> JustTypeRef:
         raise NotImplementedError(msg)
 
     def __str__(self) -> str:
-        return f"{self.module}.{self.name}"
+        return str(self.to_type_var())
 
     @classmethod
     def from_type_var(cls, typevar: TypeVar) -> ClassTypeVarRef: